I don't agree. The problem with grades is that they actually don't mean anything. They indicate nothing about a student other than how they responded to questions, at an arbitrary date and time, against how an arbitrary instructor graded those responses. For everyone who understood the game, it didn't matter. For everyone who doesn't understand the game, it probably doesn't matter.
After education, there is a world of "pass/fail" tests where sometimes passing or failing doesn't matter and the rules are foggy. Some people become well adjusted, productive, members of society and their community and some don't with many shades in between. But those aren't things that can always be taught let alone graded. You can maybe grade yourself (if you have the maturity to do so objectively) and your boss and peers may grade you, as may your SO/spouse, but those scores are have real world value and are based on real world criteria. That criteria can't be prepped for and forgotten next week, but has to be part of who you are. If you're passing those tests, you're doing something right, if not, you need to adjust. No amount of schooling (I specifically didn't use "education" there) adequately prepares you for that. Experience and introspection does.